A lot of the problems have to do with Ultrasn0w in general. I believe the problem has to do with the way Ultrasn0w hooks into CommCenter on boot of the phone. Commcenter needs to load first before Ultrasn0w does so that it can register with the network. After that Ultrasn0w can load to create the unlock.

After Ultrasn0w is installed and you power off the phone like normal Commcenter doesn't get a chance to register correctly with the network hence the broken VVM and MMS on AT&T. Ultrasn0w blocks it.